The goal of the proposed research is to investigate the mechanisms underlying the olfactory receptor processes of the primary chemoreceptor neurons as they related to the host-seeking and oviposition behavior of mosquitos. We will use the techniques of electrophysiology, analytical chemistry, and immunohistochemistry to identify and characterize the lactic acid/receptor process and its relationship to the mode of action of repellents. We also will identify and characterize the physiological properties of the receptors responsible for the discrimination of oviposition attractants.